Technological jumps

-

From time to time we witness significant changes on how things are done. In terms of how we listen to music in the last ten years I've seen several interesting changes.

Ten years ago I bought my wife her first MP3 player: It was Diamond Multimedia with 32 MB (yes, Megabytes) that could hold a couple CDs of 128kbps MP3 music. Since then on I've bought many other MP3 devices for my household. However, that marked the end of traditional media (CD-audio) for our portable uses.

While MP3 players have been around for quite a while, it seems that Apple's iPod is now the king. And while kingdoms do not last long in this market I guess Apple has done something right.

Many people (like myself) are device-centric. For quite a while I favored Creative players and while I've never bought music from iTunes, I've bought some software there. Meanwhile I've stopped buying from Creative after problems with several players.

And now that I have time I've played a bit with another thing that could change the way we listen to music at the computer. In the same line as Napster and Audiogalaxy helped people to download music from each other and later where shutdown for copyright infringement. Spotify presents us a compelling service that delivers music to us from a huge selection, I mean huge, over the Internet. Their service is not about downloading files but streaming on-demand music to your computer.

Spotify had a catch that prevented me to use it more: It only worked on Windows and OSX. However, it works over wine too. So that means Linux users can happily use the windows binary.

I know this is old news for many, but till now I did not have the time to learn more about Spotify. Whether you use the free service (that contains some ads) or the fee-based one (ad-free) the system is easy with a clean interface. It just works.

Apparently, Spotify is not available in USA. I'm sure the agreements for not being sued haven't been signed yet. I guess Spotify business is going to be based on the fees collected from subscribers and commercials (both on the UI and the audio of free service). So I really would like them to succeed as they seem to be offering yet a new way of doing a business that till now proved quite elusive: Recording Industry seemed to oppose to any change to the status quo. However, while doing that they are putting every time more and more on the edge of extinction.

Give Spotify a try and listen to some old or new music.

There seems to be an iPhone version coming soon.

Comments

Post a Comment

Popular posts from this blog

VFD control with Arduino using RS485 link

-
Image
Variable Frequency Drives ( VFD ) allow the control of spindles so speed can accurately be controlled and a detailed acceleration profile for the spindle and reverse rotation can all be handled. In essence a VFD is an three phase inverter for three-phase AC motor. I am using a popular (I mean cheap) Chinese VFD and though the reference manual is not great, I could see there is a built-in RS-485 port. I usually control the start, stop and speed selection using the keyboard on the unit but I thought it will be more useful if I could control everything from the same Arduino is doing our CNC table control. Some cheap RS-485 off eBay and some lines of code later, I can start, stop and change the speed from an Arduino. What a cool thing to have! Some configuration of your VFD are needed before you can use it like that.  You need to set PD163=1 (I am using address 1 in the code). PD=164=1 (for setting serial to 9600bps) and PD165=0 (for using ASCII and 8N1 character format)
Read more

How to get sinusoidal s-curve for a stepper motor

-
Image
After some experimentation, and delving a bit into the math of motion, I realized there can be a significant difference on the motion of a machine by just making small changes. A common and popular approach to smooth one axis of motion is to use a trapezoidal speed pattern, where acceleration and deceleration are uniformly accelerated movements (aka constant acceleration motion) separated by a portion happening at cruising speed. The problem comes with the fact that, while that approach is simple to understand and to code, it does contain sudden changes in the acceleration, that show as spikes on the acceleration derivative, called jerk. These sudden changes in the acceleration translate into undesired vibration in our machines. Most of that can be eliminated by selecting a motion pattern that does not contain sudden changes of acceleration. If we chose a mathematical function for our speed whose second derivative is continuous, then we reduce system vibration quite a lot. One ma
Read more

Stepper motor step signal timing calculation

-
Image
While we use stepper motors in many devices, the timing of the step signals is not always well understood. Most of us can see how a fixed speed is a bad idea unless the speed of motion is really slow, but it is fixed speed what is really to generate with simple code. You just can use the Arduino Blink example to send a fixed frequency of pulses to a stepper motor driver. If too slow, just reduce the delay value. But for most real-life applications variable speed controls will perform better. These systems will speed up the motor to a given maximum speed and it will slow it down to stop at the desired step count. But understanding the math behind this process is sometimes not obvious. Let us start with the simple case of the so-called trapezoidal speed motion profile. Here motion takes place in three phases: acceleration, constant speed (cruising) and deceleration. But the point is how can our code create such a behavior. Stepper motor drivers usually accept two signals to control
Read more